Call-distributing telephone-exchange system.



S. H. BROWN I].

CALL DISTRIBUTING TELEPHONE EXCHANGE SYSTEM.

APPLIOATION FILED APR. 3. 1905.

Patented May 4, 1909.

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UNITED STATES PATENT .FIDNEY HAND BROlYNll, Or- PI'YISBURG,PENNSYLVANIA, ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRA Pll COMPANY, ACORPORATION OF l\'l i\\ YORh.

CALL-DISTRIBUTING TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent. Anvlication filed April 3, 1905. SerialNo. 253,545.

Patented May 4, 1909.

To all whom it may concern:

Be it known that I, SIDNEY IIAND BROWNE, a citizen of the United Statesof America, and resident of Pittsburg, county of Allegheny,

. and State of Pennsylvania, have invented a new and useful Improvementin Call-Distributing Telepl'ione-Exchange Systems, of which thefollowing is a specification.

My invention pertains to call distributing telephone exchange systems.

In the general system, for which the improvements constituting mypresent invention are particularly designed, the entire e. change may besaid to be built up of two classes of units, line units and trunk units.Each line unit consists of a telephone line having at its substation enda telephone, and at its central olliceend two switching elements which Iwill designate respectively as a connecting element and a call receivingelement. The connecting element is an automatic swltch which is thrownmto movement by the removal of thesubstation teleboard. Each trunk unitconsists generally of a speech transmitting portion terminating at oneend in Waiting contacts, which latter are multipled to the automaticswitches of a plurality of telephone-lines; said trunk unit terminatesat its other end in a connecting element consisting of a )lng adaptcd tobe inserted in a switchboar jack at the called telephone line.

A centraloieratofs telephone, busy test connections whereby theswitchboard jacks of engaged telephone lines afl'ord a busy signal whentested with a trunk plug, and supervisory signaling means, are nrovided.It will therefore be understood that in such a system the removal of thereceiver at a telephone substation originates a call; that in responseto this removaLofi-he receiver the automatic switch of said telephoneline 'will automatically connect the line with a disengnged trunk; thatan operator in attendance upon that trunk takes the calling subscribersorder in the usual way and thereupon completes the connection byinserting the trunk plug in a switchboard ach ol' the called telephoneline.

The improvements constituting my present invention relate to theconstruction, combinations and arrangements oi apparatus and circuits(particularly at the central otlice) of systems such as outlined above,with the object principally of simplifying and minimizing the electricaldevices, instrumentalitics and circuits constituting thesystem, at. thesame time all'ording maximum elliciency ol operation under the varyinand exacting conditions of commercial telep lOIllO service.

These improvements may be readily understood from the detaileddescription which follows, wherein reference is made to the accompanyingdrawing illustrating what I be lieve to be the preferred embodiment ofthe invention. I

Referring to the drawing, and in order to afford at the outset a generalidea of the structure illustrated, a line unit is shown (at the left)the principal parts thereol being the telephone line conductorssubstation telephone 3, switchboard jacks 7 connected in multiple, andautomatic s itch S; with these parts there are associated variousrelays, resistances, circuits and connections (shown at the left-handside of the drawinglfully explained hcrcal'tcr. interrupter 2'6 arccommon to all lines tcrminating at the central ollicc. trunk unit (shownbetween the line unit at the lcl't and another line unit at the extremeright) has. as its principal parts, wailing contacts 21, 22 and 23 ofswitch 8, and similar contacts at other similar switches of other lines,a plug 12$), and conductors lcading from the plug to the waitingcontacts; with these parts are associated various relays, lamps, keys,condensers, and circuit connections, all fully ex )lainedhcrealtcr.BattcryGT and call signal generator 135 are common to all-ol' the trunksof the exchange.

The mechanical details ol the automatic switch 8 form no part of thepresent invention, and hcnrc general reference thcrcto wilh sullicc.There are upon the marhet many forms of step-by-step switches, andr-UlllO forms of contimtpus-niotion switches. in which mo able terminalsare propelcd from The battery (57 andrec position of rest.

contact to contact, or from set to set of contacts, bye1ectr1cal ormechanical action; the mechanisms of many, if not all, of such switchesare suitable for and-may be readily em loyed in a system such as hereindescribed. n all such switches, when a set of movable contacts reachesa'set of fixed contacts the individual movable contacts make electricalconnection with the respectively located individual contacts of thefixed set reached, there, being a plurality offixed sets waiting to beswiped over by the movable contacts. From this relation existing betweenthe fixed and movable contacts, the term wipers is a convenient one forthe movable terminals and the term waiting contacts is a convenient onefor the fixed points. In such switches an electromagnet moves the wipersor causes them to be moved, and another electromagnet restores them orcauses them to assume their original position of rest.

The automatic electric switch, shown at 8 consists of ratchet wheel 14on a shaft 16 under tension of volute spring 15, adapted to be advancedstep by step through an angle of one step by driving pawl 49 u on eachenergization of magnet 5, and to e returned to its position of rest uponthe energization of magnet 4. Holding pawl 50 retains the switch in itsadvanced ositions. Magnet 4,

when energized, with raws both pawls 49 and 50 from engagement withratchet wheel 14 permitting spring 15 to return the pawl to The shaft 16carries a set of three wipers 1 1,-1213, and the frame of the switchcarries a plurality of sets of waiting contacts of which one set isshown at 21-2223. The interrupter 26 is shown in the circuit of magnet5, the purpose of the interrupter being to alternately denergize andreen'ergiz'e the magnet 5 when the circuit through that magnet is closedat. all other points, thus propelling the shaft 16 through successivesteps. Pin 25 attached to a moving part of the automatic switch engagesone member of the electrical switch 17 and separates the two members'inthat switch when the shaft 16 and other moving parts are in their normalpositions of rest (as shown in the drawing), the switch 17 being closedat the first step of themoving part and remaining closed until broken bythe restoration of the switch to normal.

To the waiting contacts 21-22.23, are. 'cbnnected conductors 54-6263having a trunk equipment as shown, and having also extensions164-.165-166 reaching to sets of waiting contacts (similar to 212223) ofother automatic switches similar to that herein described, but servingother tele hone lines, thus making each trunk accessi le to a pluralityof telephone lines in addition to having a lurality of trunks accessibleto each telephone line. The multiple switchboard jaeks .700 fortelephone line 1, are

. conductor 1 around resistance 18, includes the windin of a line relay19. The conductors of telep one line 40 have similar connections; oneleads to an armature 37 which normally re'sts against its back contact,and from the latter a conductor 38 leads to ground the other leadsthrough a resistance 18 to the upper member 36 of a double armaturewhich member normally rests against its back contact, and a shuntconnection 101 around resistance 18 includes the winding of a relay notshown. A conductor 71 leads from the front contact of armature 37 towiper 11, and a conductor 72 leads from front contact of armature 36t0wiper 12.

46 is' a cut-off and connecting relay for telephone line 1, having oneof its two windings connected ina conductor 60 leading magnet is 'movedfrom its back contact into engagement with its front contact.

43 is a similar cut-ofi and connecting relay for telephone line 40;conductor 74 leads from the sleeve contacts of j a'cks 42 through one ofthe two windings of said relay, to. ground. Relay 43 when energizedattracts its armature 37 and the two members 36 and 136 of its doublearmature away from theirback contacts into engagement with their frontcontactsl A conductor 35 leads from the back contact of armature 36 toone poleof the common battery 67, the other pole of which is connectedto ground by conductor" 200. A branch 39 from conductor 35 leads mentwith their front contactsi When thus retracted armature 44 engages aback con- I tact from which conductor81 leads to switch 17. From thefront contact of armature 44, conductor 45 leads to armature 136, andfrom back contact of the latter conductor 47 'leads through winding ofmagnet 5 to inter- Conductor 48 from the latter rupter 26. joinsconductor 87 from one ole of battery 67.. A conductor 52 leads rom thefront contact of armature 51 through resistance 27, one winding of relay46 and thence by conductor53 to testing wiper 13. Conductor59 .114 of akev 33 leads from the front contact of armature 136 through resistance24 and joins conductor 60. A similar conductor 59 (at the right-handside of the drawing) leads from the front contact of armature 136through resistance 24 to conductor 74. A conductor 58 branching fromconductor 35, leads to mechanism of the trunk, as hereafter explainedHaving thus described the circuit connections and mechanism at thecentral station end of the telephone line 3, 1 will next explain thecircuit connections and mechanism of the. central station trunks, onlyone of which is shown in the drawing. From waiting contact 23, or thetesting terminal of the trunk, as it may he called, conductor 54 leadsto the back contact of an armature 55 of a re,- lay 6. A-conductor 56extends from said armature and relay to the back contact of one member57 ofa double armature of relay 7. Armature 55 is normally, i. when itstrunk is not busy, retracted into engagementwith its back contact.

l rom the waiting contact. 22,-a conductor 62 leads through a condenser28 to a contact A branch 61, from conductor 62, leads through one of twowindings of relay 6 to conductor 58. From the waiting contact 21,conductor 63 leads through condenser 28 to contact 115 of key 33. Branch64' leads from conductor 63 through a second winding of relay 6 toconductor 87.

32 is a key, he movable contacts of which are connectedto branches 78,79 of conducto'rs 62 and 63 respectively, by which key the centraloperator may connect her telephone set 34 with the calling subscribeflsline for the purpose of ascertaining the party with whom connection isdesired, and by which said central operator may, should it be desired,also converse with a subscriber even it not called by anothersubscriber.

The switch plug 29 at one end of the trunk has three plug contacts, oneconnected by conductor 175 to a movable switch member 11601 a key- 33;another connected by conductor 174 to a second movable switch mem her117 of said key; and a third contact connectcd by a conductor 73, which7 extends through the winding of a relay 7, to conductor 58. The polesof signal current generator 135 are connected with back contacts adaptedto be engaged by movable switch members 116 and 1 17 respectively, uponoperation of the signaling key 33.

265 is a branch leading from conductor 64 to armature 65 of relay (3;:said armature is normally retracted into engagement with its backcontact, from which conductor leads to the front contact of an armature($6 of 11*- lay 7. A comluctor (38 leads from the front contact ofarmature 65 to the back contact of armature (S6, and a conductor 121leads from the latter thro gh signal lamp 230 to conductor 58.

A branch 76 leads from conductor 87 to armature 276 of relay 9; saidarmature is normally retracted into engagement with its back contact,from which a conductor 70 leads through a signal lamp 231 to the frontcontact of armature 69. Conductor 58, heretofore referred to, connectsto armature 69, while conductor 87 connects to the other armature 57 ofthis double armature. Relay 9 has two windings, one connected in aconductor 77 extending between conductors 5b and 78, and the otherconnected in conductor 80 extending between conductors S7- and 79.

Having thus described the. mechanism and circuits in their normalinactivepositions in which they are shown in the drawing. I will nowdescribe the operation of the systen'i in responding to a call,initiated by the subscribcr at substation 3 by the removal of hisreceiver from its switch book. The removal .of this receiver from itshook closes circuit through the electrical contacts of that hook andcurrent flows from grounded battery 67 through elements 35-3tj; at thispoint the current divides, the major port-ion flowing throughresistances 29, and the minor por tion through element 101 and windingof 19; continuing, the full current flows through elements 13137-38 togroundfen ergizing relay 19. Relay 19 attracts its armatures 51 and 44and current flows from battery 67 through elements 35-39- 44- 45 13647and windin of magnet 526 48S7-20()- to the ot ier pole of the battery,energizing magnet 5, when circuit is closed through interrupter 26, and,detinergizing magnet 5 when circuit is open at in terrupter 26, thusalternately energizing and decnergizing magnet 5, and stepping the,wipers 11, 12 and 13 forward until they make contact witlrwaitingcontacts 21, 22 and 23 of a non-busy trunk line (a non-busy line beingone, as more fully explained hereafter, in which the armature 55 ofrelay 6 and the armature 57 of relay 7 both rest against their backcontacts, the position shown in the drawing), when circuitis-established for current from battery (37 through elements 35--39-5152-27 one winding of relay 46 53 13 23 -5455-5ti57--S7--IZ()U backto the battery, thus energizing relay 46. This cnergization of relay 46causes it to attract its armaturcs, the movement of armature 136interrupting the circuit through magnet 5, thereby preventing furtherstep of battery 67 through elements 3558 61 dition in which said relays,or either of them,

which connection is necessary to permit the placed upon the waitingcontacts ('oarticu any other calling line to connect with said alsoestablishing conditionsfwhereby said upon the test rings of the jacks700 by pro- I ducing upon them a potential above the earth I equal to aportion of the potential of the bat- I tery 67. Relay 46 by attractingits armatures 36, 37 against their front contacts makes connection withconductors 7 2 and 71 to wipers 12, 11, respectively, which wipers arenow in electrical engagement with waiting contacts 22 and 21,respectively; thus path is furnished for current from one pole and onewinding of relay 6-.62 2212- 73-36-101 and winding of relay 191 31-37-7111 21 63 64 and the other Winding of relay 687200 to the other poleof the ba y,ther ebymaintaining the energization of re ay 19, by a pathofi cur rent diflerentfrom that by which said relay was originallyenergized, and also energizing relay 6 causing it to attract itsarmatures 55 and 65. By the attraction of armature 65 signal lamp 30 iscaused to glow by current from one pole of battery through elements35-58- 421 and lamp 3O66-68-265 64,87200' back to the other pole ofthebattery; and by the attraction of armature 55, conductor 54, itsbranch conductor 164 and waiting contacts connected with the latterconductor at the automatic switches of other telephone lines, aredisconnected and isolated from the connection to onepole of the batteryby way of said armature 55,

original energization of the relay 46 of any other line which mayinstitute a call while this particular trunk is engaged. Energization ofrelay 7 in the manner hereafter explained, and the consequent withdrawalof armature 57 from its back contact will also disconnect and'isolateconductor 54 from its said ground connection, the completion of whichlatter requires that armatures 55 and 57 shall simultaneously engagetheir back contacts; By this attraction of either 01' both armatures55and 57 away from their back contacts, a busy test, to wit, thatconhold their said armatures attracted, is thus larly upon the testingcontact 23) of the selected trunk, to prevent theautomatic selec tion ofthat trunk by the automatic switch of any other calling line.

It will thus be seen that the act of the calling subscriber at 3 inlifting his receiver from its hook-lever, automatically effects, byarapid succession of operations, the connection of the calling lihe witha non-busy trunk, and the establishment of conditions whereby saidcalling line and the trunk selected will both test busy, making itimpossible for trunk during the maintenance of the busy test conditionestablished in the trunk, and

outfit 34 with the calling-subscribers telephone over the followingpath: from the upper movable contact of key 32, elements 79 63 and2821'-1.17l371-31l8 36721222 62 and 28to the-lower movable contact ofkey32; one side of this connection is joined to one pole of the batterythrough elements 77 and. one winding of relay 95835, while the otherside of said connection is joined to the other pole of the battery byelement 80 and the other winding of relay 9-87- 200. Talkin connectionsare thus established b which t 1e central operator takes the callingsubscribers 'order. The central operator thereupon selects and testsjack 42 of the called telephone line, and finding the line not busyinserts her plug 29 from one pole of grounded battery 67, elements35-5873 and winding of relay 7 -74one winding of' relay 43 to ground.

This circuit energizes relays 7 and 43, the former attracting itsarmature 66, thereby opening the circuit which caused lamp 30 to glow,and the relay 43 attracting both its armaturcs 36 and 37, therebyisolating line 40 from its automatic switch equipment, not shown. Relay7 also attracts its armatures or double armature 69 and 57, therebyestablishing path for current through lamp 31 by the followingelemcnts-from one pole of battery 6735-5869-70 and lamp 31 276 7687-200to the other pole of said battery,j;hereby causing lamp 31 to glow as asignal to the operator that the telephone receiver at substation 41 ison its hook-lever. The operator then actuate/s her key 33, therein saidjack. A circuit is thus completed byconnecting signaling generator135with the line of the called subscriber and ringing the signal-bell atthe telephone substation 41;

The central operator having released her ringing-key 33, and the calledsubscriber having removed his receiver from its hook-lever, circuit isclosed for current from one pole of battery 67, through elements 35-5877and one winding of relay 9-7, l 141 17 174-404-1 -40175-l18' l'l57980-and the other winding of relay 987- 200to the other pole of saidbattery; relay 9 is thereby energized and byattracting its armature 276opens the circuit throu h lainp 31 and extinguishers, the latter, thusindicatscriber.

in to the central operator that the called su scriber has removed hisreceiver to answer the call. Lamps and 31 being thus both darkened, andthe calling and called parties being connected for conversation, thecentral operator gives the connection no further attention until theglowing of those lamps for disconnection. The conversation circuitbetween the calling and called subscribers may be traced by'thefollowing elements: from calling subscribers telephone 3, elements 1183672-12-22-62 and 28114-117-17440through the telephone ll of the calledsubscriber4()-175 116-115G3 and 28-2l11-71-37 1 back to the telephone 3of the calling sub- The sides of this connection are connected to therespective poles of common battery 67 from one pole of said batter byelements 58from which-latter t ere are two paths, one path by element 61and one winding of relay 6 to conductor 62 at one side of condenser 28,and the other path by element 77 and one winding of relay 9 to condnctor 62 at the other side of said condenser.

From the other pole of said battery the connection extends by elements20O87from which latter there are two paths, one by element 6% andwinding of relay 6 to conductor 63 at one side of condenser 28, and theother path by element 80 and wiruling of relay 9 to'conductor 63 at theother side of condenser 28.

Conversation having been completed, the hanging up of thetelephone-receiver at substation 41 lI1t61IU)l'.S the circuit heretoforetraced through t o windings of relay 9, thereby deiinergizing saidrelay, which releases its armature to again close the pre viou'slytraced circuit by which lamp 31 was caused to glow. Upon the hanging upof the telephone-receiver at substation 3, the circuit previously tracedthrough the windings of relay 6 is interrupted, thereby deenergiiingsaidrelay, which releases its armatures, armature acting to againestablish the previously traced circuit by which lamp 30 was caused toglow. The opening of circuit at substation 3 breaks the circuitpreviously described as having continued thecncrgization of relay 19,and the release of arn'rature 44 the moving )art of the switc l 17 toopen the latter, there 1y interruptingthe circuit last traced above, anddeenergnnng magnet 4.

The release of armature 44 above referred to, also opens the circuitfrom said armature to conductor 45, by which relay 46 was ener- 'ized,there-by denergizing said relay. The hanging-up of the receiver atsubstation 3 therefore acts automatically to restore to their normalpositions (illustrated in the drawing) all parts of the central ofiiceequipment individual to line 1. But following the replacement upon theirhook-levers of the receivers of both the calling and called lines,

whereby both lamps 30 and 31 are caused to glow as signals to thecentral-station operator, a brief interval of time will necessarilyelapse before the central 0 era-tor removes her plug '29 from theswitchoard jack of the called line. During this interval, the busytest,preventing connection of other calling telephone lines with thisparticular trunk, should be maintained, otherwise confusion may resultfrom connecting such a calling line with a trunk whose )lug is insertedin the jack of a tele hone su scriber who is not the one desired thecalling arty. The means for the maintenance of tlie busy-test upon thetrunk during this period is an important part of the present invention.At this stage of the operation the denergization of relay 6 has-causedit to release its armature 55, thereby closing at that point thepreviously traced path from conductor 54 to ground but as relay 7 isstill'energized, attracting its armatures, said path to ground is stillopen atarmature 57. The armature 57 is thus held out of contact withconductor 56, and continues the busy-test upon the t. anl; until theenergizing circuit of relay 7 is interrupted by removal of plug 29 fromjack 4.2. lamps 3(Tand 31 are now glowing before the central operator asa signal for removal of her plug 29 in response to these signals saidoperator removes this plug, whereby relay 43 is deenergized releasingits armatures, which restore connection of line 40 with its automaticswitch-equipment, not shown. Removal of the plug also breaks theenergizing circuit of relay 7, which, by releasing its armatures,permits armature 57 to engage its back-contact, thus restoring the trunkto its non-busy condition and establishing conditions whereby theautomatic switch of any calling telephone line may effect connectionwith said trunk. I

The establishment of the busy-test by ar mature 57, while a plug such as29'is in a jack, such as 42, attains another desirable and necessaryresult in permitting the central operator, attendant upon plug 29, touse that plug to communicate by means of her key 32, with any telephoneline for which no call has been received, without danger of interruptionfrom a calling telephone line. This is effected by simply inserting herplug 29 into a jack 42 of the line of the subscriber It will beremembered that the signal

